In a conventional organic light emitting device (OLED) and a method of fabricating the same, a thin film transistor (TFT) circuit and a light emitting device are disposed on a substrate orderly to form a display device. The display device is then sealed by a cover plate to prevent moisture from entering the display device. As a result, the light emitting device is not damaged by moisture. Because the fabrication processes of the TFT and the light emitting device are performed orderly on the same substrate, the yield rate of the substrate is obtained by multiplying the yield rate of the TFT by the yield rate of the light emitting device, which is far less than the individual yield rates. Recently, the TFT and the light emitting device are fabricated on different substrates to increase the yield rate, the aperture ratio and the reliability of the organic light emitting display. Then, the two substrates are assembled together to form the display.
FIG. 1 is a cross-sectional, exploded view of a conventional organic light emitting device 100 formed by assembling two substrates. The organic light emitting device 100 includes a first substrate 10 (also known as a TFT substrate) and a second substrate 20 (also known as an OLED substrate). Several switching transistors (not shown in FIG. 1), driver transistors 12 and electrical connecting units 14 are formed on the first substrate 10. The electrical connecting units 14 are used for providing signals to the pixels on the second substrate 20. A light emitting device is formed on the second substrate 20 and includes, in each subpixel such as R, G, B, a first electrode 21, a light emitting layer (for example, for emitting red light, green light and blue light, respectively) 22, and a second electrode 25. An insulating layer 23 isolates the light emitting layer 22, the first electrode 21 and the second electrode 25 in each subpixel from the adjacent subpixel(s). A barrier wall 24 is used for isolating the second electrode 25 in each subpixel from the adjacent subpixel(s).
The organic light emitting display 100 is formed by assembling the first substrate 10 and the second substrate 20. The electrical connecting units 14 on the first substrate 10 are electrically connected to sources or drains of the driver transistors 12. Therefore, after the two substrates are assembled together, the sources or the drains of the driver transistors 12 on the first substrate 10 are electrically connected to the pixel electrodes, e.g., the second electrodes 25, of the second substrate 20 through the electrical connecting units 14, for providing the light emitting device of the second substrate 20 with image signals.
When the two substrates are assembled together, the electric connecting units 14 directly contact the light emitting device in light-emitting regions, designated at R, G and B in FIG. 1, of the second substrate 20. Therefore, the light emitting device is easily damaged, and the yield rate is lowered.